1. Field of the Invention
The present invention relates generally to a method for performing handoff in a mobile communication system and a system thereof, and more particularly, to a method capable of seamlessly and efficiently performing handoff of a data service between the different types of network access systems and a system thereof.
2. Description of the Related Art
Wireless communication systems have been developed for situations in which it is not possible to connect a fixed wired network up to a terminal. With the progress of the communication technology, the wireless communication system has developed into the mobile communication system.
The 4th generation mobile communication system supports ultrahigh-speed multimedia service beyond the 1st generation analog system, the 2nd generation digital system, and the 3rd generation IMT-2000 system supporting the high-speed multimedia service.
Among the 3rd generation mobile communication systems, the typical mobile communication system having a channel structure for high-speed data transmission includes a 1x Evolution Data Only (1xEVDO) system. The 1xEVDO system is a system using a Code Division Multiple Access (CDMA) scheme. A configuration of the common 1xEVDO system will be described with reference to FIG. 1. The 1xEVDO system includes a Packet Data Service Node (PDSN) 101, connected to the Internet 100, for transmitting high-speed packet data to Access Networks (ANs) 103, and a Packet Control Function (PCF) 102 for controlling the ANs 103. The ANs 103 each wirelessly communicate with a plurality of access terminals (ATs) 104, and transmit the high-speed packet data to the AT having the highest data rate.
The 4th generation mobile communication system evolved from the 3rd generation mobile communication system, such as the 1xEVDO system, aims at a data rate of 20 Mbps or higher for the ultrahigh-speed multimedia service, and uses the orthogonal frequency in transmitting signals like the Orthogonal Frequency Division Multiplexing (OFDM) scheme. The typical example of the 4th generation mobile communication system can include the Worldwide Interoperability for Microwave Access (WiMax) system, the standardization of which is now in progress in Institute of Electrical and Electronics Engineers (IEEE). A configuration of the common WiMax system will be described with reference to FIG. 2. The WiMax system includes Base Stations (BSs) 202, each of which wirelessly communicates with a plurality of terminals 203 and supports the ultrahigh-speed multimedia service, and an Access Service Network (ASN) 201, connected to the Internet 200, for transmitting high-speed packet data to the BSs 202.